Cathode and cathode connector



Oct. 22, 1957 J. P. STELMAK 2,810,852

CATHODE AND CATHODE CONNECTOR Filed NOV. 1, 1951 lNV N OR bggz]? United States Patent CATHODE AND CATHODE CONNECTOR John P. Stelmak, Forest Hills, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application November 1, 1951, Serial No. 254,316

4 Claims. (Cl. 313-332) This invention pertains to a cathode structure and a method for making the same.

Heretofore, in the manufacture of tubular cathodes, the cathode was connected to its lead and terminal by means of a tab or connector secured to the body of the electrode. When such cathode elements were manufactured, the cathode connector was attached after the main body of the component had been completely formed, and such connection was effected by welding or some similar operation. Because of the delicate structure of the cathode, any operations so performed increase the possibility of distortion of the desired shape of the element' through jolting and jarring and thereby upsetting the relationship to be established between the cathode and the other elements of the tube. Furthermore, if heat is applied during the course of any operation in the formation of the cathode and attachment of the cathode connector, undesirable internal stresses may be set up.

It is desirable to have a connector of low heat conductivity to reduce heat losses from the cathode sleeve since heat loss may be a serious problem, particularly in smaller cathodes. However, one solution of this problem normally requires that the connector be made of a different material than the usual nickel sleeve, for example Nichrome. With this combination of materials, welding then becomes a problem since these metals do not weld easily.

The principal object of this invention, therefore, is to provide a novel construction of a cathode and cathode connector which is exceedingly strong and durable.

A further object of this invention is to provide a cathode which is simple in construction and easy to manufacture.

Another object of this invention is to provide a method of fabricating a cathode of the type described which is speedy and eflicient and which subjects the cathode to a minimum number of forming operations.

A still further object of this invention is to provide a method of constructing a cathode which does not require any subsequent operation to attach the connector.

Another object of this invention is to provide a cathode having a low heat conductivity connector attached thereto in a manner which eliminates the need for welding.

In general, these and other objects, which will become apparent as the description proceeds, are achieved by forming a strip of sheet metal into a hollow body with the end edges arranged to interlock and to provide a longitudinal reinforcing joint or seam for the cathode. An intermediate step in the fabrication consists in placing the cathode connector wire or metal strip in contact with one of the said end edges so that when the interlocking joint is formed, the connector wire becomes an integral part of such joint.

The invention will now be described in detail with continuous reference to the drawing, wherein Figs. 1, 2, 3 and 4 represent steps in the fabrication of the cathode, and Fig. 5 represents a side view of the completed cathode.

In the first step in the operation of forming a cathode according to this invention, a strip of sheet metal 1 which ice A may be wound on a spool from which it is fed or which may be fed from any other convenient source (not shown), is passed through a guide 3 and wound or wrapped around a mandrel 5 so that the leading edge 9 of the metal strip is disposed adjacent to the main body of the metal strip 1. To form the desired longitudinal overlapped joint, the leading edge of the metal is bent downwardly as viewed in Figure l, at a relatively sharp angle with respect to the portion of the metal strip wrapped on the mandrel so that a portion 15 of the metal extends parallel to the main body of the metal strip. A cathode connector 7 which may be in the form of a ribbon or wire of any suitable material, may be wound on a spool from which it is fed or it may be fed from any other convenient source (not shown). The connector is laid on the bent portion 15 of the metal strip in the recess formed by the bending of the leading edge 9 of such strip so that the connector extends parallel with the longitudinal axis of the mandrel and beyond the end of the body of the cathode.

The next step consists of cutting the desired length of sheet metal strip from the spool (not shown) and folding the newly cut edge 17 to enclose the leading edge 9 and the superposed connector 7 and crimping the parts together to form an interlocking longitudinal joint or seam 13 parallel to the longitudinal axis of the cathode cylinder 11.

The final operation consists of pressing the longitudinal joint 13 flush against the main body of the cathode 11 with the cathode connector 7 firmly positioned in the joint.

A side view of the completed cathode is shown in Fig. 5, wherein is illustrated the relationship between the cathode connector 7 and the longitudinal joint 13 formed of the two interlocking edges of the strip of sheet metal. The cathode is rigidly mounted within the tube in its appropriate relationship with the other components of the tube and the connector 7 is connected to its proper place in the alternating current circuit of the tube in any desired manner.

What is claimed is:

1. The method of forming a cathode structure which comprises bending a strip of sheet metal having a relatively high coefiicient of heat conductivity into a curvilinear form, positioning a connector strip having a relatively low coefiicient of heat conductivity adjacent an edge of said metal, and subsequently folding the edges of said metal together to form an interlocking joint in which is incorporated a substantial portion of said connector strip.

2. A method of forming a cathode structure comprising wrapping a strip of sheet metal having a relatively high coefiicient of heat conductivity around a mandrel; bending one end edge of said strip of metal at an angle with respect to the wrapped portion of said strip; inserting a cathode connector strip having a relatively low coefficient of heat conductivity into the recess formed by said bend, said connector extending along said strip and beyond one end thereof; cutting said strip of sheet metal to the desired length; and bending the cut edge of said strip of sheet metal around said one end edge for interlocking said two bent end edges to form a reinforced longitudinal joint containing said connector strip, whereby said cathode is adapted to be connected to a circuit element through said connector strip, with reduced heat loss from said cathode.

3. A cathode structure comprising a sleeve made of a metal of relatively high heat conductivity and having a lockseam extending axially parallel therewith, said lockseam including at least two folds of the material of said sleeve, and a sheet metal connector engaged frictionally only between said two folds and extending beyond an having relatively low heat egnductivity.

4. A cathode structure cornpi ising an elongated sleeve made of one metaland aneleetr-ical vconnector i'na de of a inetal difier en t fromsaid one metal, said connector being fixed 'frietidna'lly only "to an end portion of said sleeve and having a portion extending from saidend portionuof eaid sleeve. f

UNITED STATES PATENTS Kershaw Nov. 12, 1940 

